A tricyanoethylated pentaerythritol of the formula: EQU HOCH.sub.2 C(CH.sub.2 OCH.sub.2 CH.sub.2 CN).sub.3
has usually been produced by reacting 1 mole of pentaerythritol of the formula: C(CH.sub.2 OH).sub.4 with 3 moles of acrylonitrile, for example, by Michael Addition Reaction in an alkaline aqueous medium. The tricyanoethylated pentaerythritol is usually used for producing a high dielectric polymer containing a cyano group, which comprises mono-esterifying the tricyanoethylated pentaerythritol with acrylic acid or methacrylic acid and homopolymerizing or copolymerizing one or more of the resulting cyanoethyl group-containing (meth)acrylic ester monomers optionally with other copolymerizable monomer, or alternatively graft-polymerizing the cyanoethyl group-containing (meth)acrylic ester monomers with other polymer (cf. JP-A-5-140234, JP-A-5-140235, JP-A-6-263825, and JP-8-134149=U.S. Ser. No. 08/558,776 filed on Nov. 15, 1995, and now U.S. Pat. No. 5,777,038). The high dielectric polymer is usually used as an organic electronic material, such as a binder for an organic dispersion-type electroluminescense device or a dielectric material for a film condenser (cf. JP-A-6-336506, and JP-A-8-134149=U.S. Ser. No. 08/558,776, and now U.S. Pat. No. 5,777,638).
The tricyanoethylated pentaerythritol is usually produced by Michael Addition Reaction of pentaerythritol and acrylonitrile as mentioned above, more specifically, by subjecting the starting materials to Michael Addition Reaction in an alkaline aqueous solution, extracting the produced tricyanoethylated pentaerythritol with an appropriate solvent (e.g. methylene chloride), separating the phase of the extraction solvent from the reaction system, neutralizing the extract and then washing it with water, or alternatively washing the extract with water until it becomes neutral, and finally distilling the extract thus treated.
However, according to the conventional method, there are produced various by-products such as mono-, di- and/or tetra-cyanoethylated products in addition to the desired tricyanoethylated pentaerythritol, which cause lowering of the yield and purity of the desired tricyanoethylated pentaerythritol. Even though the reaction is carried out by using the most suitable molar ratio of the starting pentaerythritol and acrylonitrile at the best reaction conditions, the obtained tricyanoethylated pentaerythritol has a low purity, for example, a purity of upto 50 to 55%. Besides, since tricyanoethylated pentaerythritol has a high molecular weight and a high boiling point, it is very difficult to purify by a conventional method such as distillation, and hence, in order to obtain a product having a purity of 90% or more, it is necessary to treat the product with a column filled with an adsorbent such as silica gel, which is disadvantageous in view of a high cost.